Luo Li-Lin, Qu Xiang-Long, Li Zheng, Li Xia, Sun Hao-Ling
Department of Chemistry, Capital Normal University, Beijing, 100048, China.
Dalton Trans. 2018 Jan 15;47(3):925-934. doi: 10.1039/c7dt04024e.
A series of the anhydrous lanthanide-based metal-organic frameworks (Ln-MOFs) were successfully synthesized under hydrothermal conditions of Ln(iii) ions with 3,4'-oxybis(benzoate) (3,4'-oba), oxalate (ox) and 1,10-phenanthroline (phen). Structural analyses revealed that they are isostructural 3D open-frameworks with the formula of [Ln(3,4'-oba) (phen)(ox)] (Ln = Sm for 1, Eu for 2, Gd for 3, Tb for 4, and Dy for 5) and the topology of {3·4·5·6}. Within the 3D structure, the [LnON] units are bridged by ox to form [Lnox] dimers and then are further connected by 3,4'-oba ligands. These complexes feature high chemical stabilities in common solvents, boiling water, and acidic (pH = 3) and alkaline (pH = 13) solutions and high thermal stability even up to 400 °C. The photoluminescence and magnetic properties were studied. Especially, 2 shows bright red emission with a high luminescence efficiency of 40.51%. We mainly discuss the luminescence properties of 2 in common solvents and inorganic ions. It shows luminescence stability in common solvents and the ability to detect ammonia and Fe ions under a long excitation wavelength (350 nm). Significantly, magnetic studies reveal that the Dy-MOF, 5, shows a typical single-molecule magnetic behavior. Under zero dc field, compound 5 shows temperature and frequency dependent out-of-phase (χ'') signals, indicating the existence of slow magnetic relaxation.
在水热条件下，利用3,4'-氧双（苯甲酸）（3,4'-oba）、草酸盐（ox）和1,10-菲咯啉（phen）成功合成了一系列无水镧系金属有机框架材料（Ln-MOFs）。结构分析表明，它们是同构的三维开放框架，化学式为[Ln(3,4'-oba)(phen)(ox)]（Ln = 1为Sm，2为Eu，3为Gd，4为Tb，5为Dy），拓扑结构为{3·4·5·6}。在三维结构中，[LnON]单元通过ox桥连形成[Lnox]二聚体，然后通过3,4'-oba配体进一步连接。这些配合物在常见溶剂、沸水中以及酸性（pH = 3）和碱性（pH = 13）溶液中具有高化学稳定性，甚至在高达400°C时仍具有高热稳定性。研究了其光致发光和磁性性质。特别是，2发出亮红色发射光，发光效率高达40.51%。我们主要讨论了2在常见溶剂和无机离子中的发光性质。它在常见溶剂中表现出发光稳定性，并且在长激发波长（350 nm）下具有检测氨和铁离子的能力。值得注意的是，磁性研究表明，Dy-MOF 5表现出典型的单分子磁行为。在零直流场下，化合物5显示出与温度和频率相关的异相（χ''）信号，表明存在缓慢的磁弛豫。
